Complex-forming poly-schiff&#39;s bases



United States Patent "ice ififfjli 3 481 904 table. This table illustrates the ability of the metals of 7 s the first and second subsidiary groups of the periodic sys- COMPLEX-FORMING POLY-SCHIFFS BASES Ernst Bayer, Melanchthomstrasse 33, tern to combine with the polycondensates of this invention.

Tuebingen, Germany N0 Drawing. Filed Aug. 26, 1966, Ser. No. 575,239 fi Claims priority, application Germany, Oct. 28, 1965, Percent or G. atom/100 g. or theoretical poly-Sohifisbase Int. Cl. C08g 9/06; C221) 11/04 US. Cl. 260-72 3 Claims 0 0 23.9 6.13 5.5 0.02 ABSTRACT OF THE DISCLOSURE h 2 A poly-Schiffs base consisting essentially of recurring units of the formula The ability of the complex-former to combine with 15 gold is extremely high and better than that of all the CH CH hitherto known complex-formers. Theoretically it is equivll SH HS H; alent to 2 gram-atoms of gold per molecule unit, i.e.,

394 g. of gold per 388 g. of complex-former. This capac- Hs N N SH ity is also achieved in practice.

l| In addition, it is possible to remove the gold which has accumulated on the complex-former, for example by Whfirell} 15 an Integer Of and a Pf for treatment with an acid, so that the polycondensate accord- Pfoduclng the Same y condensing ing to the invention can be used as an ion-exchanger mercaptobenzene and at least a stoichiometric amount of ifi f l 111 i glyoxal, effecting the reaction in an aqueous solution at The gold is advantageously removed from the coma tempefatum of about plex-forrner by treatment with hydrochloric acid, for

example, by shaking with 4 N hydrochloric acid. The acid is preferably contacted with the complex for a pro- This invention relates to a poly-Schififs base which l d t t ti f up t 12 hours. can be used as speclfic complex form Of 1011 exchanger Any metal residues still adhering to the complex-former for gold. after such a treatment can be removed by treatment with It is known Bayef f Aflgewandte Chemie sodium or potassium cyanide. The material may then be 76 76 (1964)] that it is possible, by polycondensing 2,5- d again to ab orb gold,

diaminothiophenol and glyoxal, to Obtain a p y These methods of recovering the gold result in concen- Sate p y corresponding to Formula trated gold (III)-salt solutions, more specifically in complex salt solutions. The metallic gold has to be recovered SH HS H from the solutions obtained according to known methods.

In another method of recovering the gold the charged N N complex-forming poly-Schiffs base is heated to a temperature above about 250 and up to 600 C. The organic CHCH n material is destroyed in this heating process and the gold This material is able to form complexes with metal is recovered in metallic form. As the poly-Schiflfs base ions, particularly those of the first and second subsidiary has a very high capacity of absorbing gold, the amounts groups of the periodic system, and to release them again. of this polymer used are rather small. Therefore, destroy- It has now been found that improved polycondensates ing these absorbing agents may be more economical then can be obtained by polycondensing l,4-diamino-2,5-dias expensive recovering process.

mercaptobenzene and glyoxal in aqueous solution at tem- The polycondensate is insoluble in the conventional peratures in the range from 40 to 90 C. The following organic solvents, for example, alcohols, ethers, dimethyl general formula may be attributed to these polyconr formamide, acetone, chloroform, benzene and hydrocardensates. bons, and also in water. It is resistant to weak acids and weak alkaline liquors.

CH- i l SH 118- r -i EXAMPLE 1 r Preparation of the poly-Schiffs base from 1,4-diamino- HS N N SH 2,5-dimercaptobenzene and glyoxal 3.5 g. (0.014 mol) of thoroughly purified 1,4-diamin0- In this formula, n is a number greater than Y10 and may 2,5-dimercaptobenzene dihydrochloride were dissolved be as high as 2,000, preferably in the range of about 20 with continuous stirring in 70 ml. of distilled water to about 200. through which nitrogen was bubbled. To prepare the To prepare this polycondensate, the glyoxal is preferfree diamine, 14 ml. of a 12% by weight soda solution ably used in an amount equivalent to that of the 1,4- were added dropwise to the solution in a stream of diamino-Z,S-dimercaptobenzene or in an excess of up to nitrogen S0 that the P 0f e l e s o t 10 times the stoichiometrically necessary quantity. 7. Following complete neutralisation, the brownish-green The polycondensate according to the invention isa comsolution was heated to 60 C. in a paratfin bath, after plex-forrner which is practically specific for gold (III) which 8.8 g. (0.06 mol) of 40% by weight aqueous ions and is therefore suitable for isolating gold (III) ions glyoxal solution were added dropwise to it at this temfrom dilute solutions, even if these solutions contain other perature in a stream of nitrogen. After all the glyoxal metal ions. solution had been added, the product was stirred for The material only combines with metals of the first another half hour at 60 C. and cooled to 0 C., and and second subsidiary groups of the periodic system, the precipitated brownish-green product suction-filtered.

gold being very much preferred as shown by the following It was briefly boiled in 50 ml. of boiling water, suctionfiltered again and washed with 20 ml. of hot water. The polycon-densate was dried over diphosphorus pentoxide for 20 hours at room temperature/ 14 mm. Hg. The poly- Schifis base was obtained as a brownish-green finegrained powder. Yield=2.4 g. (86% of the theoretical).

To remove acid-soluble components, the poly-SchifiYs base was stirred for 20 hours at room temperature in 0.1 N hydrochloric acid. The product was then suctionfiltered and successively washed three times with ml. of distilled water, 10 ml. of methanol and 10 ml. of ether and then dried over diphosphorus pentoxide at C./ 14 mm. Hg until its weight was constant.

EXAMPLE 2 1 m1. of a 0.01 molar solution of zinc sulphate, 1 m1. of cadmium acetate, 1 ml. of mercury (II) acetate, 1 ml. of copper acetate and 1 ml. of tetrachloro-gold (III)- acid, were mixed together and made up to 1 litre with distilled water. 1 g. of poly-Schilts base, obtained as in Example 1, was added to this solution which was then shaken for 12 hours at room temperature. The macromolecule was then filtered off, after which the metal contents both of the filtrate and of the macromolecule are determined. Whereas the gold quantitatively combined with the macromolecule, the copper (II)-, cadmium and zinc ions remained quantitatively in the solution. Only about one tenth of the mercury originally introduced also combined. The macromolecule was found to have combined with 1.92 mg. of gold (98%), 0.22 mg. of mercury (11%) and less than 0.002 mg. each of copper, cadmium and zinc.

mg. of gold-containing poly-Schiffs basewere shaken for 12 hours at 20 C. with 300 ml. of 0.1 N hydrochloric acid. of the gold was released to the solution under these conditions.

To remove the remaining gold, the product was shaken for 3 hours with 100 ml. of a 0.01 N sodium cyanide solution.

Iclaim:

1. Poly-Schilfs base consisting essentially of recurring units of the formula II N l-SH 118- I HS Ifil N SH Villa...

References Cited UNITED STATES PATENTS 12/ 1946 Auten et a1.

9/1953 Brooke.

WILLIAM H. SHORT, Primary Examiner L. M. PHYNES, Assistant Examiner US. Cl. X.R. 

